The elements for Iron Photographer 20:
1 - one to five stones
2 - something green
3 - sunlight
I don't think anybody will need to have the first element, one to five stones, defined. I hope the second element, something green, is equally self-explanatory. The final element, sunlight is the simplest of all.
The only question I can anticipate for IP20 is whether or not one (or more) of the stones can also be the green element. The answer to that is sure, why not?